Method and apparatus for interference mitigation in wireless networks

ABSTRACT

Methods and apparatuses are provided that include mitigating interference for devices communicating with femto nodes or other low power base stations by assigning protected resources for communicating therewith. The protected resources can be negotiated with a macrocell base station using interference cancellation. The protected resources can be assigned based on an early or late handover event, which can indicate that the device may be susceptible to interference from the macrocell base station.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.13/232,883, entitled “METHOD AND APPARATUS FOR INTERFERENCE MITIGATIONIN WIRELESS NETWORKS” filed Sep. 14, 2011, which claims the benefit ofU.S. Provisional Application Ser. No. 61/384,163, entitled “JOINT RADIORESOURCE MANAGEMENT AND INTERFERENCE MITIGATION PROCEDURES FOR WIRELESSNETWORKS” filed Sep. 17, 2010, each of which are assigned to theassignee hereof and hereby expressly incorporated by reference herein intheir entirety.

BACKGROUND

1. Field

The following description relates generally to wireless networkcommunications, and more particularly to considerations for mitigatinginterference.

2. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as, for example, voice, data, and soon. Typical wireless communication systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing available system resources (e.g., bandwidth, transmit power, . .. ). Examples of such multiple-access systems may include code divisionmultiple access (CDMA) systems, time division multiple access (TDMA)systems, frequency division multiple access (FDMA) systems, orthogonalfrequency division multiple access (OFDMA) systems, and the like.Additionally, the systems can conform to specifications such as thirdgeneration partnership project (3GPP) (e.g., 3GPP LTE (Long TermEvolution)/LTE-Advanced), ultra mobile broadband (UMB), evolution dataoptimized (EV-DO), etc.

Generally, wireless multiple-access communication systems maysimultaneously support communication for multiple mobile devices. Eachmobile device may communicate with one or more base stations viatransmissions on forward and reverse links. The forward link (ordownlink) refers to the communication link from base stations to mobiledevices, and the reverse link (or uplink) refers to the communicationlink from mobile devices to base stations. Further, communicationsbetween mobile devices and base stations may be established viasingle-input single-output (SISO) systems, multiple-input single-output(MISO) systems, multiple-input multiple-output (MIMO) systems, and soforth.

To supplement conventional base stations, additional restricted basestations can be deployed to provide more robust wireless coverage tomobile devices. For example, wireless relay stations and low power basestations (e.g., which can be commonly referred to as Home NodeBs or HomeeNBs, collectively referred to as H(e)NBs, femto nodes, pico nodes,etc.) can be deployed for incremental capacity growth, richer userexperience, in-building or other specific geographic coverage, and/orthe like. In some configurations, such low power base stations can beconnected to the Internet via broadband connection (e.g., digitalsubscriber line (DSL) router, cable or other modem, etc.), which canprovide the backhaul link to the mobile operator's network. Thus, forexample, the low power base stations can be deployed in user homes toprovide mobile network access to one or more devices via the broadbandconnection.

Since the low power base stations operate at a power significantly lessthan that of conventional macrocell base stations, where the low powerbase station is situated closer to a macrocell base station within acell thereof, a device near the low power base station may experienceincreased power from the macrocell base station. In this case, thedevice may never handover to the low power base station, though servicesfrom the low power base station may be desired.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In accordance with one or more aspects and corresponding disclosurethereof, the present disclosure describes various aspects in connectionwith mitigating interference among low power base stations (e.g., femtonodes), conventional base stations (e.g., macrocell base stations), anddevices communicating therewith. A macrocell base station can perform anearly handover of a device to a femto node such that the macrocell basestation power measured by the device is over a threshold as compared topower of the femto node. The macrocell base station can indicate anearly handover event to the femto node, and the femto node can selectresources for the device that are protected from interference caused bythe macrocell base station. For example, these resources can benegotiated between the macrocell base station and the femto node.Similarly, where the device is communicating with femto node, the femtonode can configure a late handover event to delay handover to amacrocell base station for the device. In this example, when a power ofthe macrocell base station increases over a threshold difference fromthe power of the femto node, the femto node can similarly selectresources for the device that are protected from interference by themacrocell base station. Thus, a device can communicate with the femtonode when there is an interfering macrocell base station.

According to an example, a method for mitigating interference in awireless network is provided. The method includes detecting a handoverevent related to a device communicating with a base station anddetermining whether the handover event is one of an early or latehandover event. In addition, the method can include assigning a set ofprotected resources for communicating with the mobile device after thehandover event, based on the handover event.

In another aspect, an apparatus for mitigating interference in awireless network is provided. The apparatus includes means for detectinga handover event related to a mobile device communicating with a basestation. The apparatus also includes means for assigning a set ofprotected resources for communicating with the mobile device based ondetermining whether the handover event is one of an early handover eventor a late handover event.

In yet another aspect, an apparatus for mitigating interference in awireless network is provided including at least one processor configuredto detect a handover event related to a mobile device communicating witha base station and determine whether the handover event is one of anearly handover event or a late handover event. The at least oneprocessor is further configured to assign a set of protected resourcesfor communicating with the mobile device after the handover event, basedon the handover event. The apparatus further includes a memory coupledto the at least one processor.

Still, in another aspect, a computer-program product for mitigatinginterference in a wireless network is provided including acomputer-readable medium having code for causing at least one computerto detect a handover event related to a mobile device communicating witha base station and code for causing the at least one computer todetermine whether the handover event is one of an early handover eventor a late handover event. The computer-readable medium further includescode for causing the at least one computer to assign a set of protectedresources for communicating with the mobile device after the handoverevent, based on the handover event.

In another example, a method for mitigating interference in a wirelessnetwork is provided including detecting a handover event related tohanding over communications of a mobile device to a base station andtransmitting a handover message to the base station indicating whetherthe handover event corresponds to an early handover event.

In another aspect, an apparatus for mitigating interference in awireless network is provided. The apparatus includes means for detectinga handover event related to handing over communications of a mobiledevice to a base station. The apparatus also includes means fortransmitting a handover message to the base station indicating whetherthe handover event corresponds to an early handover event.

In yet another aspect, an apparatus for mitigating interference in awireless network is provided. The apparatus includes at least oneprocessor configured to detect a handover event related to handing overcommunications of a mobile device to a base station and transmit ahandover message to the base station indicating whether the handoverevent corresponds to an early handover event. The apparatus furtherincludes a memory coupled to the at least one processor.

Moreover, in another aspect, a computer-program product for mitigatinginterference in a wireless network is provided including acomputer-readable medium having code for causing at least one computerto detect a handover event related to handing over communications of amobile device to a base station. The computer-readable medium furtherincludes code for causing the at least one computer to transmit ahandover message to the base station indicating whether the handoverevent corresponds to an early handover event.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed aspects will hereinafter be described in conjunction withthe appended drawings, provided to illustrate and not to limit thedisclosed aspects, wherein like designations denote like elements, andin which:

FIG. 1 is a block diagram of an aspect of a system including devicescommunicating with low power base stations and macrocell base stations.

FIG. 2 is a block diagram of an aspect of a system for assigningresources to a device based on a handover event.

FIG. 3 is a block diagram of an aspect of a system for communicating ahandover event for a device to a femto node.

FIG. 4 is a flow chart of an aspect of a methodology for assigningprotected or non-protected resources to a device.

FIG. 5 is a flow chart of an aspect of a methodology for transmitting ahandover message to a base station.

FIG. 6 is a flow chart of an aspect of a methodology for commanding adevice to generate a measurement report.

FIG. 7 is a flow chart of an aspect of a methodology for determiningresources over which to command a device to generate a measurementreport.

FIG. 8 is a block diagram of a base station in accordance with aspectsdescribed herein.

FIG. 9 is a block diagram of an aspect of a wireless communicationsystem in accordance with various aspects set forth herein.

FIG. 10 is a schematic block diagram of an aspect of a wireless networkenvironment that can be employed in conjunction with the various systemsand methods described herein.

DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofone or more aspects. It may be evident, however, that such aspect(s) maybe practiced without these specific details.

Described further herein are various considerations related tointerference mitigation for devices in wireless networks including lowpower base stations and macrocell base stations. A low power basestation can be referred to herein as a femto node, pico node, micronode, or similar base station. In particular, handover events related toa device can be detected, and a set of protected resources can beassigned to the device to mitigate interference over the set ofresources. For example, a device can be handed over from a macrocellbase station to a femto node, though the macrocell base station has amore desirable signal quality than the femto node. This can be referredto as an early handover event. In this example, the femto node canassign resources to the device that are negotiated with the macrocellbase station such to mitigate interference thereover. The resources canbe referred to herein as protected resources, interference cancelledresources, inter-cell interference coordination (ICIC) resources,enhanced ICIC (eICIC) resources, and/or the like.

In a similar example, a device communicating with a femto node can bedelayed in handing over to the macrocell base station though a signalquality difference between the macrocell base station and the femto nodeis over a threshold typically indicative of handover. For example, thethreshold can be adjusted and/or another higher threshold can be set foractually handing the device over to the macrocell base station. When thesignal quality difference reaches the threshold typically indicative ofhandover, this can indicate entry into a late handover event, and thefemto node can similarly assign protected resources to the device forcommunicating therewith until the higher threshold is reached (and/oruntil exiting of the late handover event is detected). In one example,existing event thresholds in wireless standards can be used to determinewhen early and/or late handover events are triggered (e.g., event A3, A2or A4, etc., in 3GPP LTE). In another example, a new event can bedefined for this purpose.

As used in this application, the terms “component,” “module,” “system”and the like are intended to include a computer-related entity, such asbut not limited to hardware, firmware, a combination of hardware andsoftware, software, or software in execution, etc. For example, acomponent may be, but is not limited to being, a process running on aprocessor, a processor, an object, an executable, a thread of execution,a program, and/or a computer. By way of illustration, both anapplication running on a computing device and the computing device canbe a component. One or more components can reside within a processand/or thread of execution and a component may be localized on onecomputer and/or distributed between two or more computers. In addition,these components can execute from various computer readable media havingvarious data structures stored thereon. The components may communicateby way of local and/or remote processes such as in accordance with asignal having one or more data packets, such as data from one componentinteracting with another component in a local system, distributedsystem, and/or across a network such as the Internet with other systemsby way of the signal.

Furthermore, various aspects are described herein in connection with aterminal, which can be a wired terminal or a wireless terminal. Aterminal can also be called a system, device, subscriber unit,subscriber station, mobile station, mobile, mobile device, remotestation, remote terminal, access terminal, user terminal, terminal,communication device, user agent, user device, or user equipment (UE),etc. A wireless terminal may be a cellular telephone, a satellite phone,a cordless telephone, a Session Initiation Protocol (SIP) phone, awireless local loop (WLL) station, a personal digital assistant (PDA), ahandheld device having wireless connection capability, a computingdevice, a tablet, a smart book, a netbook, or other processing devicesconnected to a wireless modem, etc. Moreover, various aspects aredescribed herein in connection with a base station. A base station maybe utilized for communicating with wireless terminal(s) and may also bereferred to as an access point, a Node B, evolved Node B (eNB), or someother terminology.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase “X employs A or B” is intended to mean anyof the natural inclusive permutations. That is, the phrase “X employs Aor B” is satisfied by any of the following instances: X employs A; Xemploys B; or X employs both A and B. In addition, the articles “a” and“an” as used in this application and the appended claims shouldgenerally be construed to mean “one or more” unless specified otherwiseor clear from the context to be directed to a singular form.

The techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and othersystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband-CDMA (W-CDMA) and other variants of CDMA. Further, cdma2000covers IS-2000, IS-95 and IS-856 standards. A TDMA system may implementa radio technology such as Global System for Mobile Communications(GSM). An OFDMA system may implement a radio technology such as EvolvedUTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are partof Universal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) is a release of UMTS that uses E-UTRA, which employsOFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS,LTE/LTE-Advanced and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). Additionally,cdma2000 and UMB are described in documents from an organization named“3rd Generation Partnership Project 2” (3GPP2). Further, such wirelesscommunication systems may additionally include peer-to-peer (e.g.,mobile-to-mobile) ad hoc network systems often using unpaired unlicensedspectrums, 802.xx wireless LAN, BLUETOOTH and any other short- orlong-range, wireless communication techniques.

Various aspects or features will be presented in terms of systems thatmay include a number of devices, components, modules, and the like. Itis to be understood and appreciated that the various systems may includeadditional devices, components, modules, etc. and/or may not include allof the devices, components, modules etc. discussed in connection withthe figures. A combination of these approaches may also be used.

FIG. 1 illustrates an example system 100 for providing mobility and/orinterference mitigation among base stations in a wireless network havingvarious classes of power. System 100 can be a heterogeneously-deployedwireless network including base station 102, which can be a macrocellbase station or similar base station (e.g., eNB) in a first power class,and base station 104, which can be a low power base station such as afemto node, pico node, micro node, etc., in a second power class that islower than the first power class. The network can further include adevice 106 (e.g., UE) that communicates with base stations 102 and/or104, and a base station 108, which can similarly be a macrocell basestation. The system 100 also includes a device 110 that can communicatewith base stations 102 and/or 108. In addition, base station 102 cancommunicate with base station 104 and/or 108 over a wired or wirelessbackhaul connection (e.g., using an X2 interface in an LTEconfiguration).

Generally, device 110 can communicate with base station 102 and can movetowards base station 108. Once device 110 is within cell coverage ofbase station 108, base station 102 can handover the device 110 (e.g., inidle or active mode) to base station 108 based on detecting one or moreevents from measurement reports received from the device 110. Forexample, the one or more events can correspond to detecting that asignal quality measurement of base station 108 is over a thresholddifference from that of base station 102. Where a femto node 104operates within a cell provided by a base station 102, mobilityprocedures can be modified as the above events may not adequatelyachieve desired communications for device 106.

For example, with conventional mobility procedures the closer femto node104 is to base station 102, the device 106 may need to be closer tofemto node 104, or at least further from base station 102 (e.g., closerto the cell edge), to be handed over to femto node 104. In this regard,thresholds for the one or more events can be modified to allow thedevice 106 to be handed over to femto node 104 sooner (e.g., where adifference in power between base station 102 and femto node 104 islarger), which can be referred to herein as an early handover event.Similarly, where device is communicating with femto node 104, the one ormore events can be modified to allow the device 106 to continuecommunicating with femto node 104 longer (e.g., where a difference inpower between femto node 104 and base station is larger) before handingover to base station 102; the time during which the difference in poweris more than an original threshold and less than the modified thresholdcan be referred to herein as a late handover event. Thus, entry into thelate handover event can occur when the difference in power is at anoriginal threshold for causing handover. This can be beneficial, forexample, where device 106 is within close proximity to base station 102.

Where device 106 is further from the base station 102 (e.g., closer tothe cell edge), the thresholds for the one or more events may not bemodified, or may be modified more slightly than where the device 106 iscloser to base station 102. Thus, where the thresholds are modifieddrastically, device 106 has more of a chance of being interfered bycommunications from base station 102 (e.g., since device 106 is closerto base station 102 and experiences higher power therefrom). In thiscase, upon handover of device 106 from base station 102 to femto node104, for example, femto node 104 can assign a set of protected resourcesto device 106 for communicating with femto node 104. The set ofprotected resources can correspond to resources negotiated between thebase station 102 and femto node 104 in ICIC, eICIC, or otherinterference cancellation schemes. Thus, where device 106 is close tobase station 102, it can avoid interference therefrom by being assignedresources not utilized by base station 102 for communicating with femtonode 104. In this example, femto node 104 can receive an indication(e.g., from base station 102 or otherwise) as to whether device 106 isearly handed over to femto node 104 (e.g., whether the one or morethresholds are modified at base station 102 to perform early handover),the degree to which the one or more threshold are modified, etc., andfemto node 104 can accordingly assign the protected resources to device106.

In a similar example, where device 106 is handed over from femto node104 to base station 102 (e.g., in late handover), femto node 104 canassign a set of protected resources to device 106 at least where thesignal quality of base station 102 reported by device is under thethreshold difference from that of femto node 104 for a late handoverevent and over a second threshold difference (e.g., the originaldifference for causing handover, or another defined threshold).Similarly, in this regard, device 106 can be protected from interferenceof base station 102. In one example, as described further herein,standardized events (e.g., event A3, A2, A4, etc., in LTE) can beused/modified to accomplish such functionality. In other examples, newevents can additionally or alternatively be defined. Moreover, thoughlow power base station 104 is referred to as a femto node 104, it is tobe appreciated that low power base station 104 can be substantially anyeNB, such as a macrocell base station, a pico node, a micro node, a homeNB or home eNB (H(e)NB), etc.

FIG. 2 illustrates an example apparatus 200 for mitigating interferencein certain mobility procedures. Apparatus 200 can be a femto node (e.g.,femto node 104) or other low power base station that can communicatewith one or more devices to provide wireless network access thereto, andcan include additional modules than those depicted. Apparatus 200 canoptionally include a resource negotiating module 202 for negotiatingresources with one or more base stations and/or a handover detectingmodule 204 for determining a device is to be handed over to apparatus200. Apparatus 200 can also include a resource assigning module 206 forallocating resources to the device to facilitate handover, and acommunications module 208 for communicating the resource allocation tothe device and/or communicating therewith over the resource allocation.Apparatus 200 can also optionally include an event determining module210 for determining occurrence of one or more events related to handingover device to another base station.

According to an example, resource negotiating module 202 can negotiateinterference cancelled resources with a source base station. Forexample, this can include negotiating the resources using ICIC, eICIC,or similar interference cancellation mechanisms such that the resourcenegotiating module 202 can receive at least a set of protected resourcesover which the source base station does not communicate with one or moredevices to ensure the resources are protected from interference by thesource base station. In one example, the protected resources can be timedivision multiplexing (TDM) resources assigned to apparatus 200. It isto be appreciated that resource negotiating module 202 can negotiatesuch resources with additional base stations, which can includemacrocell base stations, other femto nodes or low power base stations,and/or the like.

Further, in an example, handover detecting module 204 can receive ahandover message from a source base station related to a device. Thehandover message can include information to prepare apparatus 200 forthe handover. In addition, the handover message can include anindication of whether the device is being handed over early to apparatus200 (e.g., whether a signal quality of the source base station is over athreshold difference from that of apparatus 200 at the device). Inanother example, the handover message can include the difference insignal quality as reported by the device. Based on this information, theresource assigning module 206 can determine whether to assign protectedresources to the device.

For example, where the device is being handed over early from the sourcebase station and/or where an indicated signal quality difference is overa threshold, resource assigning module 206 can assign at least a portionof protected resources to the device for communicating with apparatus200. The protected resources can be a portion of those negotiated byresource negotiating module 202, a portion of a set of preconfiguredprotected resources known by the apparatus 200 and/or source basestation, and/or the like. Where the device is not being handed overearly and/or the indicated signal quality difference is not over thethreshold, resource assigning module 206 can assign non-protectedresources to the device to reserve the protected resources for earlyhandover devices, for instance. In addition, where the apparatus 200 andsource base station use a similar transmit power, resource assigningmodule 206 can also assign protected resources for uplink communicationsfrom the device that do not interfere with the serving base station toprotect the serving base station from interference by the device.

In any case, communications module 208 can communicate the resourceallocation to the device and/or communicate over the resource allocationto the device. Thus, in some cases, the device can be assigned protectedresources where interference from the source base station may bepresent. In another example, where the device is communicating withapparatus 200, event determining module 210 can determine that a latehandover event is triggered based on a signal quality of another basestation. In this example, resource assigning module 206 can similarlyassign protected resources to the device at least until another actualhandover event is triggered with a higher signal quality differencethreshold (e.g., to keep device communications with apparatus 200 for alonger period of time, as described), until exiting of the late handoverevent is detected (e.g., based on the handover detecting module 204detecting the signal quality difference is below the threshold), etc.

FIG. 3 illustrates an example apparatus 300 for mitigating interferencein certain mobility procedures. Apparatus 300 can be a macrocell basestation (e.g., base station 102) or other high power base station thatcan communicate with one or more devices to provide wireless networkaccess thereto, and can include additional modules than those depicted.Apparatus 300 can optionally include a resource negotiating module 302for negotiating resources with one or more femto nodes or other basestations. Apparatus 300 can also include a communications module 304 forcommunicating with a device, and a handover event determining module 306for detecting a handover event for the device. In addition, apparatus300 includes a handover notifying module 308 for communicating ahandover message to a femto node based on the handover event, and ahandover module 310 for communicating a handover command to the deviceto facilitate handing over the device to the femto node.

According to an example, resource negotiating module 302 can negotiateresources with the femto node using ICIC, eICIC, etc. to obtain a set ofresources over which the femto node does not communicate, and/or providea set of resources over which apparatus 300 does not communicate.Communications module 304 can communicate with a device over an assignedset of communications resources. Handover event determining module 306can detect a handover-related event for the device, which can includedetermining a signal quality of a nearby femto node is at least at athreshold difference to that of apparatus 300 at the device. Forexample, this can be based on a threshold difference that triggershandover and/or a modified threshold difference, as described.

In this example, handover notifying module 308 can send a handovermessage to the femto node to prepare the femto node for the handover.The handover message, in one example, can include an indication that thehandover is an early handover, as described, and/or an indication of thedifference in signal quality between the femto node and apparatus 300 atthe device. The femto node can use this information for determiningwhether to assign protected resources to the device, as described above.In addition, in response to determining the handover event, handovermodule 310 can command the device to handover communications to thefemto node.

In a specific example, in LTE, base stations can detect an event A3related to a device in which a neighbor cell has a signal quality thatis better than that of the serving base station, or a cell thereof, atthe device by an offset. According to 3GPP TS 36.331 Version 9.3.0, forexample, the entering condition for the event A3 can occur whenMn+Ofn+Ocn−Hys>Ms+Ofs+Ocs+Offwhere Mn is the measurement result of the neighbor cell, Ofn is thefrequency specific offset of the frequency of the neighbor cell, Ocn isthe cell specific offset of the neighbor cell, Hys is a hysteresisparameter for the event (e.g., to prevent ping-ponging handover betweenbase stations), Ms is the measurement result of the serving cell, Ofs isthe frequency specific offset of the serving frequency, Ocs is the cellspecific offset of the serving cell, and Off is an offset parameter forthe event.

Thus, handover event determining module 306 can configure a differentoffset for causing handover at the apparatus 300 by adjusting the Ocs,Ocn, and/or Off parameters. Referring to FIG. 1, for example, let Ocs ofbase station 102 be 0 decibels (dB), Ocn of base station 108 can be 0 dBand Ocn of femto node 104 can be set to 15 dB. In this example, event A3are triggered for devices 110 and 106 at different Ms and Mn offset. Onthe other hand, multiple A3 events can be configured for a device withdifferent Off values. For example, two events A3 could be configured fordevice 106, one with Off of 3 dB and a second one with Off of 15 dB. Inthis case, two events A3 can be triggered when device 106 moves frombase station 102 to femto node 104. The event A3 is usually configuredto trigger handover where signal quality, X dB (X>0), is above that ofthe serving cell for a duration of T seconds. In a homogenous network, atypical handover threshold of 3 dB can be configured between macrocellbase station 102 and macrocell base station 108.

In one example, in a heterogeneous network the event A3 may also beconfigured to trigger resource partitioning without a handover, an earlyhandover event with interference protection from the serving cell, alate handover event with interference protection from the neighbor cell,etc. For example, to extend the range of the femto node 104, the basestation 102 can configure the event A3 to trigger an early handover fromthe base station 102 to the femto node 104 and/or a late handover fromthe femto node 104 to the base station 102 with interference protectionfrom the base station 102, as described. In addition, to mitigateinterference, the base station 102 and/or femto node 104 can configurethe event A3 to trigger resource partitioning between the base station102 and the femto node 104 regardless of whether handover actuallyoccurs.

In example configurations, referring to FIG. 2 and FIG. 3, handoverevent determining module 306 can configure a negative event A3 thresholdwith a very low threshold such when entering the event A3, Mn−Ms<0 dB.For example, handover event determining module 306 can adjust the eventA3 threshold to trigger when Mn−Ms>−15 dB. In such a configuration, theevent A3 is entered when the signal quality difference between themeasurement result Mn of the neighbor cell (e.g., a cell provided byapparatus 200) and the measurement result Ms of the serving cell (e.g.,a cell provided by apparatus 300) is at or around −15 dB. In oneexample, the adjusted threshold can be below a radio link failurethreshold (e.g., approximately −10 dB in LTE). In this regard, handoverevent determining module 306 can trigger event A3 when the neighbor cellis much weaker than the serving cell, such that early handover can beineffective without interference mitigation.

An indication of early handover can be communicated by the handovernotifying module 308 to apparatus 200 over a backhaul connection, andhandover detecting module 204 can receive the indication. In thisregard, resource assigning module 206 can assign a set of protectedresources to the device for communicating therewith. The indication canbe an explicit indication of early handover, and/or can include signalquality measurements Mn, Ms, etc., along with related cell identifiersfrom which an early handover event can be determined, etc. For example,this can include a signal quality measurement from a strongest cell on agiven frequency, along with the corresponding cell identifier, fromwhich handover detecting module 204 can discern an early handover (e.g.,based on the signal quality measurement as compared to that of apparatus200). In one specific example, the indication can be in an explicitmessage from handover notifying module 308, which can be a messagetypically used in carrier aggregation to report measurement of one ormore base stations. The message can have a format similar to thefollowing specific data structure in LTE:

RRM-Config ::= SEQUENCE {  ue-InactiveTime ENUMERATED { s1, s2, s3, s5,s7, s10, s15, s20, s25, s30, s40, s50, min1, min1s20c, min1s40, min2,min2s30, min3, min3s30, min4, min5, min6, min7, min8, min9, min10,min12, min14, min17, min20, min24, min28, min33, min38, min44, min50,hr1, hr1min30, hr2, hr2min30, hr3, hr3min30, hr4, hr5, hr6, hr8, hr10,hr13, hr16, hr20, day1, day1hr12, day2, day2hr12, day3, day4, day5,day7, day10, day14, day19, day24, day30, dayMoreThan30}  OPTIONAL,  ..., [[ candidateCellInfoList-r10 CandidateCellInfoList-r10  OPTIONAL  ]] }CandidateCellInfoList-r10 ::= SEQUENCE (SIZE (1..maxFreq)) OFCandidateCellInfor10 CandidateCellInfo-r10 ::=  SEQUENCE {  --cellIdentification  physCellId-r10 PhysCellId,  dl-CarrierFreq-r10 ARFCN-ValueEUTRA,  -- available measurement results  rsrpResult-r10RSRP-Range OPTIONAL,  rsrqResult-r10 RSRQ-Range OPTIONAL,  ... }

In this example, the rsrpResult-r10 and rsrqResult-r10 can specifycertain values that indicate an early handover, and thus handoverdetecting module 204 can receive this structure, and determine earlyhandover based in part on the values, on comparing the values tothresholds, etc. For instance, handover detecting module 204 can comparea rsrpResult-r10 and/or rsrpResult-r10 of apparatus 300 (which providesthe serving cell in this example) to that of apparatus 200 (whichprovides the neighbor cell in this example). Related cell identifiers,such as the physCellId-r10, can be used to differentiate measurements ofapparatus 300 from those of apparatus 200 and/or other measurements, forexample. Handover detecting module 204 can determine the strongestmeasurement, which can be that of apparatus 300 in this example. Thus,where the signal quality measurements for apparatus 300 are greater thanthose for apparatus 200, this can indicate an early handover to theneighbor cell.

A device, as generally described in reference to FIG. 2 and/or FIG. 3can refer to a device 106, for example. Similarly, apparatus 200 canrefer to a femto node 104, and apparatus 300 can refer to a base station102, and both can be referred to as a serving or neighbor cell invarious examples presented below. For example, both the data and thecontrol downlink resources can be protected at the neighbor cell for thedevice upon early handover. In one example, TDM of the resources can beused to negotiate interference cancelled protected resources. If theserving cell and the neighbor cell have similar transmit power, resourceassigning module 206 can assign protected resources for uplinkcommunications as well based on a detected early or late handover event.

In another configuration, where the device is communicating with aserving cell of apparatus 200 and considering handover to a neighborcell of apparatus 300, the event determining module 210 can configure ahigh event A3 threshold such that the event A3 condition triggers whenMn−Ms>>0 dB (e.g., Mn−Ms is greater than 4 dB or Mn−Ms is greater than 8dB to 10 dB). For example, event determining module 210 can trigger theevent A3 condition when Mn−Ms>15 dB. In this case, the neighbor cell isstronger than the serving cell. To maintain the reliability of the linkbetween the device and the serving cell before a late handover event,resource assigning module 206 can similarly configure the device withprotected resources that experience no or at least a lower level ofinterference from the neighbor cell.

In this example, both the data and the control downlink resources can beprotected for the device for communications from apparatus 200. TDM ofthe resources is one example of resource protection. If the serving celland the neighbor cell have similar transmit power, resource assigningmodule 206 can assign protected resources to the device to protect theuplink resources at the neighbor cell from interference from the devicesserved by apparatus 200 in the serving cell. If the serving cell has amuch lower transmit power than the neighbor cell, resource assigningmodule 206 can assign protected uplink resources to the device toprotect the uplink resources at apparatus 200 from interference bydevices served by the neighbor cell, since the late handover event canoccur when the devices are close to the serving cell.

In other examples, handover event determining module 306 can configureevent A2 and/or event A4 defined for LTE mobility to modify behavior ofevent A3. For example, handover event determining module 306 can preventthe handover with interference protection/mitigation upon the event A2in which the signal quality of the serving cell (e.g., a cell ofapparatus 300) is below a threshold (condition: Ms+Hys<Thresh) and/orthe event A4 in which the signal quality of a neighbor cell (e.g., acell of apparatus 200) is above a neighbor threshold (condition:Mn+Ofn+Ocn−Hys>Thresh). Where a device is limited by thermal and/orambient interference, for example, removing the dominant interferencemay not lead to a substantial gain in the signal to interference plusnoise ratio (SINR). In the case of handover, where handover eventdetermining module 306 determines the serving cell is below an absolutethreshold (e.g., 3 dB compared to thermal), handover to a weaker cell inrange expansion may not be triggered.

For example, if the event A2 is triggered when Ms<3 dB, and then theevent A3 is triggered when Mn−Ms>−15 dB, handover event determiningmodule 306 can avoid performing an early handover of the device from theserving cell to the neighbor cell, as the measurement result Mn of theneighbor cell is less than the neighbor threshold (e.g., −12 dB). Inanother example, where handover event determining module 306 does notdetect triggering of event A4 (e.g., the measurement result Mn is −8 dBwhere event A4 is triggered with Mn>−5 dB), and then the event A3 istriggered when Mn−Ms>−15 dB, handover event determining module 306 canavoid performing an early handover of the device from the serving cellto the neighbor cell. In both of these examples, it can be expected thatthe downlink SINR at the neighbor cell after handover may be thermallylimited even without interference from the serving cell.

Similarly, when the serving cell, which can be provided by apparatus 200in this example, is below an absolute threshold (e.g., −6 dB compared tothermal), event determining module 210 may not trigger handover forrange expansion against a stronger neighbor cell. For example, if theevent A2 is triggered when Ms<−6 dB, and then the event A3 is triggeredwhen Mn−Ms>15 dB, event determining module 210 may trigger the events,though the events may not result in a late handover of the device fromthe serving cell to the neighbor cell, as −6 dB can be close to radiolink failure, the neighbor cell has sufficient signal strength, andtherefore the serving cell can handover the device to the neighbor cellwithout holding onto the device for a late handover to the neighborcell. For another example, if event determining module 210 determinestriggering of event A4 (e.g., Mn>−9 dB), and then of event A3 whenMn−Ms>15 dB, the triggering of the events should not result in a latehandover of the device from the serving cell to the neighbor cell, as −6dB can be close to radio link failure, the neighbor cell has sufficientsignal strength, and therefore the serving cell can handover the deviceto the neighbor cell without holding onto the device for a late handoverthereto.

In yet another example, handover event determining module 306 canconfigure a new event for determining mobility and/or interferencemanagement conditions based on a comparison of the measurement result ofa neighbor cell relative to the sum of interference from cells otherthan the serving cell. Moreover, handover event determining module 306can use such events to trigger measurement reporting from the device(e.g., through a request from handover module 310). For example, where areceived signal strength indicator (RSSI) represents the total receivedpower over the measurement bandwidth on reference signal (RS) symbols,and a RS received power (RSRP) represents the received RS power from acell over the measurement bandwidth on RS symbols, a value Δx can bedefined as follows:Δx=RSRP_x/(RSSI−RSRP_serving*N)where RSRP_x is the RS power for cell x, RSRP_serving is the RS powerfor the serving cell, and N is an estimated data and pilot to pilotpower ratio. The minimum and maximum value of N can be 1 and 3,respectively, for a system that utilizes 2 transmitters. For example,the estimate can be derived from the network or by the device. Using theminimum and maximum value for N can be plausible in many scenarios.

An alternative metric is to compare the strongest neighbor with thesecond strongest neighbor. As such, the metric Δx can be defined asRSRP_1/RSRP_2, where RSRP_1 is the RSRP of the strongest neighbor, andRSRP_2 is the RSRP of the second strongest neighbor. Where the strongestneighbor is sufficiently higher than the second strongest neighbor, itis likely that the received power from the neighbor is significantcompared to the total ambient interference plus thermal. In any case,based on the new metric Δx, handover module 310 can trigger ameasurement report at the device if Δx goes above a first threshold T1(e.g., with entering condition Δx>T1) or if Δx goes below a secondthreshold T2 (e.g., with exiting condition Δx<T2). Upon receiving themeasurement report, handover event determining module 306 can determinewhether a handover or interference mitigation event is triggered, asdescribed. In addition, based on comparing Δx to a threshold, theresource negotiating module 302 can trigger resource partitioning with aneighbor cell if the neighbor cell becomes strong compared to theambient interference.

For intra-frequency measurement, a device can arbitrarily sample thesubframes to measure as long as the performance requirement issatisfied. In a heterogeneous network with TDM partitioning, themeasurement quality over subframes can vary. For RS received power(RSRP), in the case of colliding RS, the RSRP measurement of a weakercell is likely to be consistent over all subframes. In the case ofnon-colliding RS, the RSRP measurement of a weaker cell is likely to betime varying over subframes. The RS received quality (RSRQ) can bedefined as RSRP/RSSI. RSSI can be time varying cross subframes dependingon traffic load. The RSRQ measurement hence has the variability of bothRSRP and traffic load.

In this example, handover module 310 can configure the device to reportmeasurements of other cells such that variability of the measurements istaken into account. For example, if it is desirable to be conservativeand keep legacy device out of the range expansion region, handovermodule 310 can configure the device to generate measurement reports overcolliding RSs where the signal quality of the neighbor cell can be lessgiven interference from the serving call. If it is desirable to keeplegacy devices on the protected resources, handover module 310 canconfigure the device to generate measurement reports over non-collidingRSs where the device can experience a strong signal from the neighborcell.

Moreover, a noisy RSRP measurement of the serving cell under highinterference may have a positive bias. Averaging of clean and noise RSRPmeasurements over time can also have a positive bias. As such, handoverevent determining module 306 can remove the bias when reporting fromlegacy device is received to determine whether a handover event istriggered. Handover event determining module 306 can additionally, inone example, analyze fluctuation of measurements to apply a larger Hysvalue when the measurement report varies.

FIGS. 4-7 illustrate example methodologies relating to mitigatinginterference in wireless communications. While, for purposes ofsimplicity of explanation, the methodologies are shown and described asa series of acts, it is to be understood and appreciated that themethodologies are not limited by the order of acts, as some acts may, inaccordance with one or more embodiments, occur concurrently with otheracts and/or in different orders from that shown and described herein.For example, it is to be appreciated that a methodology couldalternatively be represented as a series of interrelated states orevents, such as in a state diagram. Moreover, not all illustrated actsmay be required to implement a methodology in accordance with one ormore embodiments.

FIG. 4 depicts an example methodology 400 for mitigating interference indevice mobility.

At 402, a handover event related to a mobile device communicating with abase station can be detected. In one example, the handover event can bea LTE event, such as event A3, A2, A4, and/or other events in otherwireless network technologies, a new event, etc. The handover event canbe detected based in part on determining occurrence of the event, whichcan be based on monitoring one or more parameters, receiving anindication of occurrence of the event, etc. In one example, the handoverevent can be determined based on monitoring a signal quality measurementof a serving base station and comparing the measurement, or a differencebetween the measurement and that of another base station, to one or morethresholds. In another example, the handover event can be determined byreceiving an indication of the event from a serving base station.

At 404, it can be determined whether the handover event is an early orlate handover event. The thresholds related to entry of the handoverevent can be adjusted to cause an early or late handover. Thus,detecting whether the handover event is early or late can comprisecomparing a signal quality difference with the serving base stationreceived from the mobile device to a modified threshold, receiving anotification from the serving base station that a handover is an earlyor late handover, and/or the like.

If the handover is an early or late handover, at 406 a set of protectedresources can be assigned for communicating with the mobile device. Theprotected resources can be a subset of those previously negotiated withthe serving base station. For example, the set of protected resourcescan be allocated for the mobile device, and an indication of assignmentcan be communicated to the mobile device (e.g., in a control messageover a control channel, such as a physical downlink control channel(PDCCH) in LTE).

If the handover event is not an early or late handover event, at 408 themobile device can be handed over. For example, where the handover eventis received from the serving base station, this can include receivinghandover of the mobile device, and can include assigning resources tothe mobile device. For example, the resources, in this example, can beselected from a set of resources other than the protected resources. Inanother example, where the handover event is detected based on one ormore measurements, handing over the mobile device at 408 can includehanding over the mobile device to another base station.

FIG. 5 illustrates an example methodology 500 for indicating whether ahandover is an early handover.

At 502, a handover event related to handing over communications of amobile device to a base station can be detected. For example, the eventcan correspond to an event A3, A2, A4, etc. in LTE or other events inother wireless network technologies, a new event, etc. In an example,thresholds related to the handover can be adjusted for performing earlyhandover of some mobile devices. In this regard, a signal qualityreported by the mobile device can be compared to a signal quality of thebase station, and the difference can be compared to a modified thresholdfor entering event A3 to determine whether to perform early handover ofthe mobile device. In addition, the base station can be a low power basestation, such as a femto node, pico node, micro node, or substantiallyany eNB or H(e)NB, for example.

At 504, a handover message can be transmitted to the base stationindicating whether the handover event corresponds to an early handoverevent. In one example, the handover message can include the differencebetween the measured signal qualities; in another example, the handoverevent can comprise an explicit indication of early handover. The basestation can utilize this information to assign a set of protectedresources, protected from interference, to the mobile device forcommunicating therewith.

FIG. 6 shows an example methodology 600 for instructing a mobile deviceto generate a measurement report.

At 602, a signal quality measurement difference can be determined basedon an RSRP of a neighbor cell measured by a mobile device. For example,the signal quality measurement difference can further be based on anRSRP of another neighbor cell, an RSSI experienced at a serving basestation, and/or the like.

At 604, the mobile device can be commanded to generate a measurementreport based on comparing the signal quality measurement difference to athreshold. For example, the command can be transmitted to the mobiledevice along with parameters related to generating the measurementreport. For example, the command can include an indication forgenerating the measurement report when the threshold signal qualitymeasurement difference is above or below one or more thresholds.

FIG. 7 illustrates an example methodology 700 for commanding a mobiledevice to create measurement reports.

At 702, a mobile device can be communicated with over a set of assignedresources. For example, this can be a set of resources assigned to themobile device upon receiving an access request therefrom. The resourcescan be assigned over a PDCCH, in one example.

At 704, it can be determined whether range expansion is desired. Forexample, this determination can be made based on whether to supportrange expansion based on a version of a mobile device (e.g., whether themobile device is a legacy device). In another example, this can be basedon a measured load. Thus, where a number of mobile devices are beingcommunicated with, it can be desirable to support range expansion forsome mobile devices to allow the mobile devices to additionally oralternatively communicate with a femto node.

If range expansion is desired, at 706 the mobile device can be commandedto generate measurement reports over resources with colliding referencesignals. In this regard, measurements of neighbor cells over theresources can be higher than over non-colliding resources. In oneexample, a specification of resources over which to measure signals canbe provided to the mobile device (e.g., over a control channelcommunication).

If range expansion is not desired, at 708 the mobile device can becommanded to generate measurement reports over resources withoutcolliding reference signals. Thus, measurements of the neighbor cellscan be negligible. Similarly, this can include communicating aspecification of the resources to the mobile device (e.g., over acontrol channel communication).

It will be appreciated that, in accordance with one or more aspectsdescribed herein, inferences can be made regarding determining whetherto assign protected resources to a device to mitigate interferencethereto, and/or the like, as described. As used herein, the term to“infer” or “inference” refers generally to the process of reasoningabout or inferring states of the system, environment, and/or user from aset of observations as captured via events and/or data. Inference can beemployed to identify a specific context or action, or can generate aprobability distribution over states, for example. The inference can beprobabilistic—that is, the computation of a probability distributionover states of interest based on a consideration of data and events.Inference can also refer to techniques employed for composinghigher-level events from a set of events and/or data. Such inferenceresults in the construction of new events or actions from a set ofobserved events and/or stored event data, whether or not the events arecorrelated in close temporal proximity, and whether the events and datacome from one or several event and data sources.

FIG. 8 is an illustration of a system 800 that facilitates mitigatinginterference among base stations and femto nodes. System 800 includes abase station 802 having a receiver 810 that receives signal(s) from oneor more mobile devices or base stations 804 through a plurality ofreceive antennas 806 (e.g., which can be of multiple networktechnologies, as described), and a transmitter 836 that transmits to theone or more mobile devices or base stations 804 through a plurality oftransmit antennas 808 (e.g., which can be of multiple networktechnologies, as described). For example, base station 802 can transmitsignals received from mobile devices 804 to base stations 804, and/orvice versa. Receiver 810 can receive information from one or morereceive antennas 806 and is operatively associated with a demodulator812 that demodulates received information. In addition, in an example,receiver 810 can receive from a wired backhaul link. Though depicted asseparate antennas, it is to be appreciated that at least one of receiveantennas 806 and a corresponding one of transmit antennas 808 can becombined as the same antenna. Demodulated symbols are analyzed by aprocessor 814, which is coupled to a memory 816 that stores informationrelated to performing one or more aspects described herein.

Processor 814, for example, can be a processor dedicated to analyzinginformation received by receiver 810 and/or generating information fortransmission by a transmitter 836, a processor that controls one or morecomponents or modules of base station 802, and/or a processor thatanalyzes information received by receiver 810, generates information fortransmission by transmitter 836, and controls one or more components ormodules of base station 802. In addition, processor 814 can perform oneor more functions described herein and/or can communicate withcomponents or modules for such a purpose.

Memory 816, as described, is operatively coupled to processor 814 andcan store data to be transmitted, received data, information related toavailable channels, data associated with analyzed signal and/orinterference strength, information related to an assigned channel,power, rate, or the like, and any other suitable information forestimating a channel and communicating via the channel. Memory 816 canadditionally store protocols and/or algorithms associated with detectinghandover events and/or assigning protected resources to one or moredevices.

It will be appreciated that the data store (e.g., memory 816) describedherein can be either volatile memory or nonvolatile memory, or caninclude both volatile and nonvolatile memory. By way of illustration,and not limitation, nonvolatile memory can include read only memory(ROM), programmable ROM (PROM), electrically programmable ROM (EPROM),electrically erasable PROM (EEPROM), or flash memory. Volatile memorycan include random access memory (RAM), which acts as external cachememory. By way of illustration and not limitation, RAM is available inmany forms such as synchronous RAM (SRAM), dynamic RAM (DRAM),synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhancedSDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).The memory 816 of the subject systems and methods is intended tocomprise, without being limited to, these and any other suitable typesof memory.

Processor 814 is further optionally coupled to a resource negotiatingmodule 818, which can be similar to resource negotiating modules 202and/or 302, a handover detecting module 820, which can be similar tohandover detecting module 204, a resource assigning module 822, whichcan be similar to resource assigning module 206, a communications module824, which can be similar to communications modules 208 and/or 304, anevent determining module 826, which can be similar to event determiningmodule 210, a handover event determining module 828, which can besimilar handover event determining module 306, a handover notifyingmodule 830, which can be similar to handover notifying module 308,and/or a handover module 832, which can be similar to handover module310.

Moreover, for example, processor 814 can modulate signals to betransmitted using modulator 834, and transmit modulated signals usingtransmitter 836. Transmitter 836 can transmit signals to mobile devicesor base stations 804 over Tx antennas 808. Furthermore, althoughdepicted as being separate from the processor 814, it is to beappreciated that the resource negotiating module 818, handover detectingmodule 820, resource assigning module 822, communications module 824,event determining module 826, handover event determining module 828,handover notifying module 830, handover module 832, demodulator 812,and/or modulator 834 can be part of the processor 814 or multipleprocessors (not shown), and/or stored as instructions in memory 816 forexecution by processor 814.

In addition, base station 802 can include a backhaul communicationmodule 838 for communicating with one or more eNBs 840 over a backhaulinterface. For example, backhaul communication module 838 cancommunicate with the eNBs 840 over a wired or wireless backhaul linkusing one or more backhaul interfaces (e.g., X2 interface in LTE). Wherethe backhaul link is wireless for example, it is to be appreciated thatbase station 802 can utilize Rx antennas 806 and receiver 810 to receivecommunications from eNBs 840, and/or Tx antennas 808 and transmitter 836to communicate signals to eNBs 840.

FIG. 9 illustrates a wireless communication system 900 in accordancewith various embodiments presented herein. System 900 comprises a basestation 902 that can include multiple antenna groups. For example, oneantenna group can include antennas 904 and 906, another group cancomprise antennas 908 and 910, and an additional group can includeantennas 912 and 914. Two antennas are illustrated for each antennagroup; however, more or fewer antennas can be utilized for each group.Base station 902 can additionally include a transmitter chain and areceiver chain, each of which can in turn comprise a plurality ofcomponents or modules associated with signal transmission and reception(e.g., processors, modulators, multiplexers, demodulators,demultiplexers, antennas, etc.), as is appreciated.

Base station 902 can communicate with one or more mobile devices such asmobile device 916 and mobile device 922; however, it is to beappreciated that base station 902 can communicate with substantially anynumber of mobile devices similar to mobile devices 916 and 922. Mobiledevices 916 and 922 can be, for example, cellular phones, smart phones,laptops, handheld communication devices, handheld computing devices,satellite radios, global positioning systems, PDAs, and/or any othersuitable device for communicating over wireless communication system900. As depicted, mobile device 916 is in communication with antennas912 and 914, where antennas 912 and 914 transmit information to mobiledevice 916 over a forward link 918 and receive information from mobiledevice 916 over a reverse link 920. Moreover, mobile device 922 is incommunication with antennas 904 and 906, where antennas 904 and 906transmit information to mobile device 922 over a forward link 924 andreceive information from mobile device 922 over a reverse link 926. In afrequency division duplex (FDD) system, forward link 918 can utilize adifferent frequency band than that used by reverse link 920, and forwardlink 924 can employ a different frequency band than that employed byreverse link 926, for example. Further, in a time division duplex (TDD)system, forward link 918 and reverse link 920 can utilize a commonfrequency band and forward link 924 and reverse link 926 can utilize acommon frequency band.

Each group of antennas and/or the area in which they are designated tocommunicate can be referred to as a sector of base station 902. Forexample, antenna groups can be designed to communicate to mobile devicesin a sector of the areas covered by base station 902. In communicationover forward links 918 and 924, the transmitting antennas of basestation 902 can utilize beamforming to improve signal-to-noise ratio offorward links 918 and 924 for mobile devices 916 and 922. Also, whilebase station 902 utilizes beamforming to transmit to mobile devices 916and 922 scattered randomly through an associated coverage, mobiledevices in neighboring cells can be subject to less interference ascompared to a base station transmitting through a single antenna to allits mobile devices. Moreover, mobile devices 916 and 922 can communicatedirectly with one another using a peer-to-peer or ad hoc technology asdepicted. According to an example, system 900 can be a multiple-inputmultiple-output (MIMO) communication system or similar system thatallows assigning multiple carriers between base station 902 and mobiledevices 916 and/or 922.

FIG. 10 shows an example wireless communication system 1000. Thewireless communication system 1000 depicts one base station 1010 and onemobile device 1050 for sake of brevity. However, it is to be appreciatedthat system 1000 can include more than one base station and/or more thanone mobile device, wherein additional base stations and/or mobiledevices can be substantially similar or different from example basestation 1010 and mobile device 1050 described below. In addition, it isto be appreciated that base station 1010 and/or mobile device 1050 canemploy the systems (FIGS. 1-3, 8, and 9) and/or methods (FIGS. 4-7)described herein to facilitate wireless communication there between. Forexample, components or functions of the systems and/or methods describedherein can be part of a memory 1032 and/or 1072 or processors 1030and/or 1070 described below, and/or can be executed by processors 1030and/or 1070 to perform the disclosed functions.

At base station 1010, traffic data for a number of data streams isprovided from a data source 1012 to a transmit (TX) data processor 1014.According to an example, each data stream can be transmitted over arespective antenna. TX data processor 1014 formats, codes, andinterleaves the traffic data stream based on a particular coding schemeselected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot datausing orthogonal frequency division multiplexing (OFDM) techniques.Additionally or alternatively, the pilot symbols can be frequencydivision multiplexed (FDM), time division multiplexed (TDM), or codedivision multiplexed (CDM). The pilot data is typically a known datapattern that is processed in a known manner and can be used at mobiledevice 1050 to estimate channel response. The multiplexed pilot andcoded data for each data stream can be modulated (e.g., symbol mapped)based on a particular modulation scheme (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM), etc.) selected forthat data stream to provide modulation symbols. The data rate, coding,and modulation for each data stream can be determined by instructionsperformed or provided by processor 1030.

The modulation symbols for the data streams can be provided to a TX MIMOprocessor 1020, which can further process the modulation symbols (e.g.,for OFDM). TX MIMO processor 1020 then provides N_(T) modulation symbolstreams to N_(T) transmitters (TMTR) 1022 a through 1022 t. In variousembodiments, TX MIMO processor 1020 applies beamforming weights to thesymbols of the data streams and to the antenna from which the symbol isbeing transmitted.

Each transmitter 1022 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel.Further, N_(T) modulated signals from transmitters 1022 a through 1022 tare transmitted from N_(T) antennas 1024 a through 1024 t, respectively.

At mobile device 1050, the transmitted modulated signals are received byN_(R) antennas 1052 a through 1052 r and the received signal from eachantenna 1052 is provided to a respective receiver (RCVR) 1054 a through1054 r. Each receiver 1054 conditions (e.g., filters, amplifies, anddownconverts) a respective signal, digitizes the conditioned signal toprovide samples, and further processes the samples to provide acorresponding “received” symbol stream.

An RX data processor 1060 can receive and process the N_(R) receivedsymbol streams from N_(R) receivers 1054 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. RX dataprocessor 1060 can demodulate, deinterleave, and decode each detectedsymbol stream to recover the traffic data for the data stream. Theprocessing by RX data processor 1060 is complementary to that performedby TX MIMO processor 1020 and TX data processor 1014 at base station1010.

The reverse link message can comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message can be processed by a TX data processor 1038, whichalso receives traffic data for a number of data streams from a datasource 1036, modulated by a modulator 1080, conditioned by transmitters1054 a through 1054 r, and transmitted back to base station 1010.

At base station 1010, the modulated signals from mobile device 1050 arereceived by antennas 1024, conditioned by receivers 1022, demodulated bya demodulator 1040, and processed by a RX data processor 1042 to extractthe reverse link message transmitted by mobile device 1050. Further,processor 1030 can process the extracted message to determine whichprecoding matrix to use for determining the beamforming weights.

Processors 1030 and 1070 can direct (e.g., control, coordinate, manage,etc.) operation at base station 1010 and mobile device 1050,respectively. Respective processors 1030 and 1070 can be associated withmemory 1032 and 1072 that store program codes and data.

The various illustrative logics, logical blocks, modules, components,and circuits described in connection with the embodiments disclosedherein may be implemented or performed with a general purpose processor,a digital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but, in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. Additionally, at least oneprocessor may comprise one or more modules operable to perform one ormore of the steps and/or actions described above. An exemplary storagemedium may be coupled to the processor, such that the processor can readinformation from, and write information to, the storage medium. In thealternative, the storage medium may be integral to the processor.Further, in some aspects, the processor and the storage medium mayreside in an ASIC. Additionally, the ASIC may reside in a user terminal.In the alternative, the processor and the storage medium may reside asdiscrete components in a user terminal.

In one or more aspects, the functions, methods, or algorithms describedmay be implemented in hardware, software, firmware, or any combinationthereof. If implemented in software, the functions may be stored ortransmitted as one or more instructions or code on a computer-readablemedium, which may be incorporated into a computer program product.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable media that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, substantiallyany connection may be termed a computer-readable medium. For example, ifsoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs usually reproduce data optically withlasers. Combinations of the above should also be included within thescope of computer-readable media.

While the foregoing disclosure discusses illustrative aspects and/orembodiments, it should be noted that various changes and modificationscould be made herein without departing from the scope of the describedaspects and/or embodiments as defined by the appended claims.Furthermore, although elements of the described aspects and/orembodiments may be described or claimed in the singular, the plural iscontemplated unless limitation to the singular is explicitly stated.Additionally, all or a portion of any aspect and/or embodiment may beutilized with all or a portion of any other aspect and/or embodiment,unless stated otherwise.

The invention claimed is:
 1. A method for mitigating interference in awireless network, the method executed by a first base station, themethod comprising: detecting a handover event related to a handover of amobile device, communicating with a second base station, to the firstbase station; determining whether the handover event is an earlyhandover event or not; and assigning a set of protected resources tomitigate interference when communicating with the mobile device afterthe handover event, if the handover event is the early handover event,wherein the handover event is the early handover event when a signalquality measurement of the second base station is greater than a signalquality measurement of the first base station by at least a thresholdamount.
 2. The method of claim 1, further comprising negotiating the setof protected resources with the second base station.
 3. The method ofclaim 1, further comprising receiving an indication, from the secondbase station, that the handover event corresponds to the early handoverevent.
 4. The method of claim 1, further comprising receiving the signalquality measurement of the second base station from the second basestation.
 5. The method of claim 1, wherein the signal qualitymeasurement of the second base station comprises a corresponding cellidentification.
 6. A method for mitigating interference in a wirelessnetwork, the method executed by a first base station in communicationwith a mobile device, the method comprising: detecting a handover eventrelated to handover of the mobile device to a second base station;determining whether the handover event is a late handover event or not;and assigning a set of protected resources to mitigate interference whencommunicating with the mobile device until exiting the late handoverevent is detected, if the handover event is the late handover event,wherein the handover event is the late handover event when a signalquality measurement of the second base station is greater than a signalquality measurement of the first base station by at least a thresholdamount.
 7. The method of claim 6, further comprising negotiating the setof protected resources with the second base station.
 8. The method ofclaim 6, further comprising receiving an indication, from the secondbase station, that the handover event corresponds to the late handoverevent.
 9. The method of claim 6, further comprising receiving at leastone signal quality measurement from the second base station, wherein thedetermining whether the handover event is the late handover event or notis based in part on the at least one signal quality measurement.
 10. Themethod of claim 9, wherein the at least one signal quality measurementcomprises a difference between a plurality of signal qualitymeasurements.
 11. The method of claim 9, wherein the at least one signalquality measurement comprises a signal quality measurement of astrongest cell on a frequency and a corresponding cell identification.12. The method of claim 6, further comprising adjusting a firstthreshold signal quality difference to a second threshold signal qualitydifference, the first threshold signal quality difference and the secondthreshold signal quality difference corresponding to different valuesfor performing late handover.
 13. The method of claim 12, furthercomprising: receiving a signal quality measurement difference from thesecond base station; and wherein the determining comprises determiningthat the handover event corresponds to the late handover event based onthe received signal quality measurement difference, the first thresholdsignal quality difference, and the second threshold signal qualitydifference.
 14. An apparatus for mitigating interference in a wirelessnetwork, the apparatus being a first base station, comprising: a memory;and at least one processor coupled to the memory, and configured to:detect a handover event related to a handover of a mobile device,communicating with a second base station, to the first base station;determine whether the handover event is an early handover event or not;and assign a set of protected resources to mitigate interference whencommunicating with the mobile device after the handover event, if thehandover event is the early handover event, wherein the handover eventis the early handover event when a signal quality measurement of thesecond base station is greater than a signal quality measurement of thefirst base station by at least a threshold amount.
 15. The apparatus ofclaim 14, wherein the at least one processor is further configured tonegotiate the set of protected resources with the second base station.16. The apparatus of claim 14, wherein the at least one processordetermines based in part on receiving an indication from the second basestation that the handover event corresponds to the early handover event.17. The apparatus of claim 14, wherein the at least one processordetermines whether the handover event is the early handover event or notbased in part on receiving the signal quality measurement of the basestation from the second base station.
 18. The apparatus of claim 14,wherein the signal quality measurement of the second base stationfurther comprises a corresponding cell identification.
 19. An apparatusfor mitigating interference in a wireless network, the apparatus being afirst base station, the apparatus comprising: a memory; and at least oneprocessor coupled to the memory, and configured to: detect a handoverevent related to handover of a mobile device to a second base station;determine whether the handover event is a late handover event or not;and assign a set of protected resources to mitigate interference whencommunicating with the mobile device until exiting the late handoverevent is detected, if the handover event is the late handover event,wherein the handover event is the late handover event when a signalquality measurement of the second base station is greater than a signalquality measurement of the first base station by at least a thresholdamount.
 20. The apparatus of claim 19, wherein the at least oneprocessor is further configured to negotiate the set of protectedresources with the second base station.
 21. The apparatus of claim 19,wherein the at least one processor determines based in part on receivingan indication, from the second base station, that the handover eventcorresponds to the late handover event.
 22. The apparatus of claim 19,wherein the at least one processor determines whether the handover eventis the late handover event based in part on receiving at least onesignal quality measurement from the second base station.
 23. Theapparatus of claim 22, wherein the at least one signal qualitymeasurement comprises a difference between a plurality of signal qualitymeasurements.
 24. The apparatus of claim 22, wherein the at least onesignal quality measurement comprises a signal quality measurement of astrongest cell on a frequency and a corresponding cell identification.25. The apparatus of claim 22, wherein the at least one processor isfurther configured to adjust a first threshold signal quality differenceto a second threshold signal quality difference, the first thresholdsignal quality difference and the second threshold signal qualitydifference corresponding to different values for performing latehandover.
 26. The apparatus of claim 25, wherein the at least oneprocessor determines the handover event corresponds to the late handoverevent based on a received signal quality difference related to thesecond base station, the first threshold signal quality difference andthe second threshold signal quality difference.